This invention relates to a protection relay, and particularly a thermal relay, capable of being connected to a contactor and including a box provided with power connection terminals on the input and output sides, and control terminals, and provided on the front with manually operated devices for actuation or adjustment. As is well known, the power terminals on the input side and the control terminals of this type of protection relay must be connected to the corresponding power and control terminals of an adjacent contactor.
The invention relates also to a protected control set including such a protection relay.
Documents EP-256 900 and EP-828 270 disclose thermal protection relays in which the box is provided with a flap that can fold down on selection, control or adjustment devices that must remain inaccessible in normal service, by pivoting or by sliding. The flap leaves a stop button and a reset button accessible at all times. The operator can thus use the stop button to freely cut off the power line through a contactor, the coil of which is connected to the thermal relay or through the reset button, he can manually reset the thermal relay into its operation state after it has tripped. On the other hand, the operator can only take action on the adjustment button or on the manual/automatic mode switch (H/A) when the flap is opened.
The power interconnection between the relay and the contactor remains hidden as long as the two devices are assembled. On the other hand, the control interconnection that the user has to make between the relay control terminals and the contactor control terminals leaves the conductors on the front of the equipment visible and accessible to be manipulated. This can be a serious problem.
The purpose of the invention is to provide a masked control interconnection for the relay and the contactor using simple means.
According to the invention, the relay box includes at least one recess setback from its front face used for the passage of an interconnection conductor between a relay control terminal and a contactor control terminal, the said recess being masked in normal service by a cache, or cover, and housing part of a prewiring additive, or accessory, provided with the interconnection conductor(s), on the front.
The cache may be a flap that enables and prohibits operation of an actuation device or a limited access adjustment device, when in the open or closed position respectively. Alternatively, the cache may simply be a fixed part of the protection relay box.
The prewiring addition may be housed in the recess, either when the recess is provided on the front of the protection relay box that can be concealed by a flap, or when the recess is provided in a fixed part of the box setback from this front face.
The invention also relates to a protected control set formed by the protection relay and the contactor laid out and interconnected as described above.